It has been proposed to form tape structures from polypropylene film that is coated with a layer of propylene copolymer including ethylene units such that the coating has a lower softening point than the core. Such tape structures are disclosed, for example, in U.S. Pat. No. 5,578,370 the teachings of which are hereby incorporated by reference in their entirety. U.S. Patent Application 2004/0242103A1 (incorporated by reference) has also proposed to form monoaxially drawn tape structures characterized by substantial draw ratios and incorporating a central layer of a polyolefin with one or two surface layers of a polyolefin from the same class as the central layer. The DSC melting point of the outer layers is lower than that of the central layer to facilitate heat bonding. Such drawn tape elements may be interwoven so as to form a mat structure which is then subjected to heat thereby fusing the tape elements in place. Multiple layers of such interwoven mat structures may be combined to form moldable structures of substantial thickness that may be shaped to three-dimensional configurations.
In addition to tape elements, there commonly exists fiber elements that are also characterized by having a lower melting surface than the main fiber component. A core/shell fiber generally consists of a core of one type of polymer, with a surface layer (also called a shell or cladding) of a different polymer. The fiber's mechanical properties are mainly a result of the core material, whereas the surface layer determines the external properties (e.g., adhesion, friction, softness). One advantage of a core/shell fiber is the ability to achieve a combination of such properties that would be impossible in a simple, homogeneous fiber. One type of core/shell fiber has a polyester core and a polyolefin shell (e.g., polypropylene). A typical application for this fiber is in nonwoven fabrics where the lower melting point of the polypropylene surface layer allows these strong polyester core fibers to be bonded together without losing their strength.
Anti-ballistics fibers and yarns tend to be expensive, leading to expensive anti-ballistics panels and impact resistant components made from the anti-ballistics yarns. The anti-ballistics panels made from unidirectional Kevlar and aramid fibers are typically embedded in a matrix. There is a need to produce a unidirectional anti-ballistics component or panel of fiber or tape elements using a lower amount of matrix material.